| SNO | Components | Description |
|---|---|---|
| 1 | Activities | They dictate the UI and handle the user interaction to the smart phone screen |
| 2 | Services | They handle background processing associated with an application. |
| 3 | Broadcast Receivers | They handle communication between Android OS and applications. |
| 4 | Content Providers | They handle data and database management issues. |
An activity represents a single screen with a user interface,in-short Activity performs actions on the screen. For example, an email application might have one activity that shows a list of new emails, another activity to compose an email, and another activity for reading emails. If an application has more than one activity, then one of them should be marked as the activity that is presented when the application is launched.
An activity is implemented as a subclass of Activity class as follows:
public class MainActivity extends Activity {
}
A service is a component that runs in the background to perform long-running operations. For example, a service might play music in the background while the user is in a different application, or it might fetch data over the network without blocking user interaction with an activity.
A service is implemented as a subclass of Service class as follows :
public class MyService extends Service {
}
Broadcast Receivers simply respond to broadcast messages from other applications or from the system.
A broadcast receiver is implemented as a subclass of BroadcastReceiver class and each message is broadcaster as an Intent object.
public class MyReceiver extends BroadcastReceiver {
public void onReceive(context,intent){}
}
A content provider component supplies data from one application to others on request.
A content provider is implemented as a subclass of ContentProvider class as follows :
public class MyContentProvider extends ContentProvider {
public void onCreate(){}
}